1. Field of the Invention
The present invention relates to a power transmission device for a vehicle.
2. Description of Related Art
Patent document 1 (JP-A-2009-1234) describes a technology for controlling a reduction gear ratio of an engine and a reduction gear ratio of an electric motor by using a planetary gear mechanism as a technology of a power transmission device of a hybrid vehicle.
According to the technology of Patent document 1, a correspondence relationship between the reduction gear ratio of the engine and the reduction gear ratio of the electric motor is fixed. That is, if the reduction gear ratio of the engine is decided, the reduction gear ratio of the electric motor is also decided to be unique. Therefore, it is impossible to select efficient operating conditions of the engine and the electric motor individually.